Hirata, Takahashi, Ikeda, Aso

Summary

Today's activities were focused on the recovery of the PRM suspension. The tasks involved checking the remaining magnets' polarity, inspecting the current state of the PRM Suspension, attempting to restore the OpLev, and planning future steps.

Magnet Polarity

We examined the polarity of the remaining magnets. For detailed findings, please refer to a separate report by Hirata-san.

PRM Suspension Inspection

Test Mass wire Breakers: We inspected whether the wires were properly seated in the grooves of the wire breakers of the test mass. Due to the challenging nature of visual inspection in this area, we utilized a smartphone to take photographs. We found that all the wires sit nicely in the grooves. 1st WB1, 1st WB2, 2nd WB1, 2nd WB2
PRM Mirror Alignment: It was observed that the PRM mirror is significantly tilted, causing the OpLev beam to miss the QPD. The beam primarily deviated in pitch, passing approximately 3 cm above the center of the first BS on the QPD baseplate.
Mirror and Recoil Mass Tilt: In the recoil mass, the mirror was significantly tilted in pitch and was in contact with the earthquake stops. The mirror and recoil mass were tilted in opposite directions. This condition could not be explained solely by the tilt of the IM.
Wire Clamp Gaps: We noted a significant gap in the wire clamp part suspending the mirror from the IM (photo). In contrast, the same part in the PR3 Suspension displayed a minimal gap (photo). We recalled that a similar issue of loosening had been addressed in PR3 but was not corrected in PRM at that time, as there was no pitch jumping issue reported for PRM. The recent earthquake might have caused the wires to slip due to the loose clamp, resulting in the significant pitch tilt in PRM. If this was what actually happened, it seems necessary to extract the suspension from the vacuum tank to properly adjust the relative tilt of the IM and RM.

OpLev Recovery Attempts

Realignment of TM through IM Tilt: We tried to realign the TM by tilting the IM in an attempt to restore the OpLev beam. The BF GAS fishing rod was used to lower the IM, but this led to one of the Horizontal OSEM flags touching and rotating due to excessive pressure.
Roll and Pitch Adjustments: After the above adjustment, a significant roll tilt in the IM was discovered and adjusted using the IM Moving Mass. Despite moving the IM Moving Mass in pitch, the OpLev beam did not move as expected. We then lightly pressed the mirror with Vectra Alpha to induce pitch movement. Subsequent adjustments resulted in the beam moving in the intended direction. However, it was determined that significant movement of the Moving Mass is required to bring the OpLev to the QPD center, which risks contact with another Horizontal OSEM flag.
Next Steps: We plan to adjust the OSEM Body as necessary while tilting the IM to bring the OpLev to the center. The subsequent steps include evaluating the tilt of the RM, the state of IM OSEMs, and experimenting with inserting the magnet stand using the Gluing Jig (without actual gluing).

Concerns and Future Considerations

Alignment Challenges: We anticipate that the RM will be significantly tilted from the horizontal when OpLev is centered, which may hinder the parallel alignment of the TM’s AR surface with the coil bobbin attached to the RM. This misalignment could prevent effective magnet adhesion.
Potential Tilt After Magnet Adhesion: Even if alignment is achieved, the added weight of the magnet post-adhesion might cause the TM to tilt in pitch, leading to a misalignment of the coil and magnet.
Possible Solution: Before deciding to extract the suspension, we plan to adjust the Earthquake Stop to align TM and RM, then adhere the magnet. We will release TM and RM afterward to assess the extent of misalignment. If the misalignment exceeds acceptable limits, we will consider extracting the suspension.